I shall be present there (at the Cistern) before you. I shall be your witness and, by Allah, I perceive as if I am seeing with my own eyes my Cistern at this very state and I have been given the keys of the treasures of the earth or the keys of the earth and, by Allah, I am not afraid concerning you that you would associate anything (with Allah after me), but I am afraid that you would be vying with one another (for the possession of) the treasures of the earth.
Sahih Muslim Book 43, Hadith 37